The purpose of the current research is to determine if the protein inductive factor called mesodermal factor (MF) and a protein synthesis initiation factor (IF-3) are the same molecule. In oder to test this hypothesis, we must be able to synthesize 125I-mRNA with completely normal structure and function and with very high specific activity, e.g., 10 to the eighth power dpm 125I/micron g RNA. Because of two unexpected technical difficulties, the production of this 125I-mRNA is just now being finished. We are also in the process of determining the nature of the changes in translational activity that may occur in early chick embryos during primary embryonic induction. At present, we are collecting mRNA from induced and non-induced embryonic fragments from 23 hr chick embryos. Once collected, we will compare the synthetic capabilities of these mRNAs using a cell-free protein synthesis system. Finally, we are testing the ability of MF to replace IF-3 stripped from the wheat embryo extracts. These experiments should give us a better understanding of the biochemical changes taking place during primary embryonic induction.